Risk factors for inadequate bowel preparation and quality improvement strategies in colonoscopy: a narrative review

Colonoscopy is the gold-standard screening test for colorectal cancer, yet its diagnostic yield relies heavily on adequate bowel preparation. Despite standard protocols, 20%–30% of procedures still have inadequate cleansing, which lowers adenoma detection, prolongs procedures, increases repeat examinations, and wastes resources. Preparation quality is influenced by multiple interacting factors: patient characteristics (age, comorbidities, medication use, adherence), regimen features (purgative type, dose, split-dose scheduling), and healthcare delivery (education quality, appointment timing). Most previous studies have examined these factors in isolation, leaving a gap in integrated, evidence-based guidance. This narrative review synthesizes current knowledge on determinants of preparation quality, with emphasis on emerging strategies such as risk-stratified protocols, low-volume purgatives, digital health tools (mobile apps, SMS reminders), and AI-based real-time assessment. We aim to provide a practical framework for individualized preparation, thereby improving both the efficiency and quality of colonoscopy-based screening.